The discovery and development of new substances and materials is a primary goal of the material sciences, of chemistry and pharmacy. However, the search for suitable compounds is often very costly and time-consuming. To be able to conduct this search more effectively and inexpensively, a systematic methodology which has become known under the name of “combinatory chemistry” had been introduced in the pharmaceutical and then also in other application fields years ago already. Here, several potentially interesting compounds are produced and analyzed in parallel. The advantage of this method is that automation is possible, which allows high processing speeds in a minimum of time.
To produce the material libraries required in this context, a large number of potentially interesting substances or their progenitor compounds must be positioned or metered at defined points of corresponding substrates. Because of the generally large number of substances to be metered, this is preferably done in a fully automatic manner. Conventional metering roboters utilize systems in which the substance to be metered is taken up by means of a syringe which is connected to a metering needle via a connection hose. The syringe as well as the connection hose and the metering needle are initially filled only with an operating fluid, the metering needle being filled with air at its end facing the metering orifice. For metering, the metering needle is dipped into the substance to be metered and the plunger of the syringe pulled out of the associated metering body. Due to the volume enlargement, the substance to be metered is drawn into the metering needle and into the connection hose. The air contained in the metering needle forms a buffer, so that contamination or mixing of the substance to be metered and the operating fluid is avoided. A disadvantage of such a metering system is that the air buffer present in the metering needle is compressible, and highly viscous media or suspensions can thus be metered only with difficulties.